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                <span class="en">What To Test</span></a>
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    <h2>
      <span class="en">Android Market Topics</span>
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          <span class="en">Application Licensing</span></a>
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              <span class="en">In-app Billing Overview</span></a>
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              <span class="en">Implementing In-app Billing</span></a>
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              <span class="en">Security and Design</span></a>
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              <span class="en">Testing In-app Billing</span></a>
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              <span class="en">Administering In-app Billing</span></a>
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              <span class="en">In-app Billing Reference</span></a>
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          <span class="en">Market Filters</span></a>
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          <span class="en">Multiple APK Support</span></a>
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  <li>
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               <span class="zh-TW" style="display:none">開發</span>
    </h2>
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        <span class="en">Introduction</span></a>
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                <span class="en">Managing Virtual Devices</span>
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            <a href="../../../guide/developing/devices/managing-avds.html">
              <span class="en">With AVD Manager</span>
            </a>
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            <a href="../../../guide/developing/devices/managing-avds-cmdline.html">
              <span class="en">From the Command Line</span>
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           <a href="../../../guide/developing/devices/emulator.html">
                <span class="en">Using the Android Emulator</span>
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        <a href="../../../guide/developing/device.html">
          <span class="en">Using Hardware Devices</span>
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            <span class="en">Managing Projects</span>
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            <a href="../../../guide/developing/projects/projects-eclipse.html">
              <span class="en">From Eclipse with ADT</span>
            </a>
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                <span class="en">From the Command Line</span>
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            <span class="en">From Eclipse with ADT</span>
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            <span class="en">From the Command Line</span></a></li>
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            <span class="en">Debugging</span>
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                <span class="en">From Eclipse with ADT</span>
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                <span class="en">From Other IDEs</span>
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              <span class="en">Using DDMS</span>
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                <span class="en">Reading and Writing Logs</span>
            </a>
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                <span class="en">Debugging and Profiling UIs</span>
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                <span class="en">Profiling with Traceview and dmtracedump</span>
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                <span class="en">Using the Dev Tools App</span>
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          9-Patch</a></li>
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            <div><a href="../../../guide/developing/tools/monkeyrunner_concepts.html">
              <span class="en">monkeyrunner</span>
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                <span class="en">MonkeyDevice</span>
                </a></li>
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                <span class="en">MonkeyImage</span>
                </a></li>
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                <span class="en">MonkeyRunner</span>
                </a></li>
            </ul>
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          <li><a href="../../../guide/developing/tools/proguard.html">ProGuard</a></li>
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  </li>

  <li>
    <h2><span class="en">Publishing</span>
        <span class="de" style="display:none">Veröffentlichung</span>
        <span class="es" style="display:none">Publicación</span>
        <span class="fr" style="display:none">Publication</span>
        <span class="it" style="display:none">Pubblicazione</span>
        <span class="ja" style="display:none">公開</span>
        <span class="zh-CN" style="display:none">发布</span>
        <span class="zh-TW" style="display:none">發佈</span>
    </h2>
    <ul>
      <li><a href="../../../guide/publishing/app-signing.html">
            <span class="en">Signing Your Applications</span>
            <span class="de" style="display:none">Signieren Ihrer Anwendungen</span>
            <span class="es" style="display:none">Firma de aplicaciones</span>
            <span class="fr" style="display:none">Attribution de votre signature <br />à vos applications</span>
            <span class="it" style="display:none">Firma delle applicazioni</span>
            <span class="ja" style="display:none">アプリケーションへの署名</span>
            <span class="zh-CN" style="display:none">应用程序签名</span>
            <span class="zh-TW" style="display:none">簽署應用程式</span>
          </a></li>
      <li><a href="../../../guide/publishing/versioning.html">
            <span class="en">Versioning Your Applications</span>
            <span class="de" style="display:none">Versionsverwaltung für Ihre <br />Anwendungen</span>
            <span class="es" style="display:none">Versiones de las aplicaciones</span>
            <span class="fr" style="display:none">Attribution d'une version à vos applications</span>
            <span class="it" style="display:none">Controllo versioni delle applicazioni</span>
            <span class="ja" style="display:none">アプリケーションのバージョニング</span>
            <span class="zh-CN" style="display:none">应用程序版本控制</span>
            <span class="zh-TW" style="display:none">應用程式版本設定</span>
          </a></li>
      <li><a href="../../../guide/publishing/preparing.html">
            <span class="en">Preparing to Publish</span>
            <span class="de" style="display:none">Vorbereitung auf die Veröffentlichung</span>
            <span class="es" style="display:none">Publicación de aplicaciones</span>
            <span class="fr" style="display:none">Préparation à la publication</span>
            <span class="it" style="display:none">Preparativi per la pubblicazione</span>
            <span class="ja" style="display:none">公開の準備</span>
            <span class="zh-CN" style="display:none">准备发布</span>
            <span class="zh-TW" style="display:none">準備發佈</span>
          </a></li>
      <li><a href="../../../guide/publishing/publishing.html">
            <span class="en">Publishing on Android Market</span>
          </a></li>
    </ul>
  </li>

  <li>
    <h2><span class="en">Best Practices</span>
               <span class="de" style="display:none">Bewährte Verfahren</span>
               <span class="es" style="display:none">Prácticas recomendadas</span>
               <span class="fr" style="display:none">Meilleures pratiques</span>
               <span class="it" style="display:none">Best practice</span>
               <span class="ja" style="display:none">ベスト プラクティス</span>
               <span class="zh-CN" style="display:none">最佳实践</span>
               <span class="zh-TW" style="display:none">最佳實務</span>
    </h2>
    <ul>
      <li><a href="../../../guide/practices/compatibility.html">
            <span class="en">Compatibility</span>
          </a></li>
      <li class="toggle-list">
        <div><a href="../../../guide/practices/screens_support.html">
          <span class="en">Supporting Multiple Screens</span>
        </a></div>
        <ul>
          <li><a href="../../../guide/practices/screens-distribution.html">
            <span class="en">Distributing to Specific Screens</span>
          </a></li>
          <li><a href="../../../guide/practices/screen-compat-mode.html">
            <span class="en">Screen Compatibility Mode</span>
          </a></li>
          <li><a href="../../../guide/practices/screens-support-1.5.html">
            <span class="en">Strategies for Android 1.5</span>
          </a></li>
        </ul>
      </li>
      <li><a href="../../../guide/practices/optimizing-for-3.0.html">
            <span class="en">Optimizing Apps for Android 3.0</span>
          </a></li>
      <li class="toggle-list">
        <div><a href="../../../guide/practices/ui_guidelines/index.html">
               <span class="en">UI Guidelines</span>
             </a></div>
        <ul>
          <li class="toggle-list">
            <div><a href="../../../guide/practices/ui_guidelines/icon_design.html">
                   <span class="en">Icon Design <span class="new">updated</span></span>
                 </a></div>
            <ul>
              <li><a href="../../../guide/practices/ui_guidelines/icon_design_launcher.html">
                    <span class="en">Launcher Icons <span class="new">updated</span></span>
                  </a></li>
              <li><a href="../../../guide/practices/ui_guidelines/icon_design_menu.html">
                    <span class="en">Menu Icons</span>
                  </a></li>
              <li><a href="../../../guide/practices/ui_guidelines/icon_design_action_bar.html">
                    <span class="en">Action Bar Icons <span class="new">new!</span></span>
                  </a></li>
              <li><a href="../../../guide/practices/ui_guidelines/icon_design_status_bar.html">
                    <span class="en">Status Bar Icons <span class="new">updated</span></span>
                  </a></li>
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                    <span class="en">Tab Icons</span>
                  </a></li>
              <li><a href="../../../guide/practices/ui_guidelines/icon_design_dialog.html">
                    <span class="en">Dialog Icons</span>
                  </a></li>
              <li><a href="../../../guide/practices/ui_guidelines/icon_design_list.html">
                    <span class="en">List View Icons</span>
                  </a></li>
            </ul>
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          <li><a href="../../../guide/practices/ui_guidelines/widget_design.html">
                <span class="en">App Widget Design <span class="new">updated</span></span>
              </a></li>
          <li><a href="../../../guide/practices/ui_guidelines/activity_task_design.html">
                <span class="en">Activity and Task Design</span>
              </a></li>
          <li><a href="../../../guide/practices/ui_guidelines/menu_design.html">
                <span class="en">Menu Design</span>
              </a></li>
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      <li><a href="../../../guide/practices/design/accessibility.html">
            <span class="en">Designing for Accessibility</span>
          </a></li>
      <li class="toggle-list">
        <div><a href="../../../guide/practices/design/performance.html">
            <span class="en">Designing for Performance</span>
          </a></div>
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          <li><a href="../../../guide/practices/design/jni.html">
                <span class="en">JNI Tips</span>
              </a></li>
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      </li>
      <li><a href="../../../guide/practices/design/responsiveness.html">
            <span class="en">Designing for Responsiveness</span>
          </a></li>
      <li><a href="../../../guide/practices/design/seamlessness.html">
            <span class="en">Designing for Seamlessness</span>
          </a></li>
    </ul>
  </li>

  <li>
    <h2><span class="en">Web Applications</span>
    </h2>
    <ul>
      <li><a href="../../../guide/webapps/index.html">
            <span class="en">Web Apps Overview</span>
          </a></li>
      <li><a href="../../../guide/webapps/targeting.html">
            <span class="en">Targeting Screens from Web Apps</span>
          </a></li>
      <li><a href="../../../guide/webapps/webview.html">
            <span class="en">Building Web Apps in WebView</span>
          </a></li>
      <li><a href="../../../guide/webapps/debugging.html">
            <span class="en">Debugging Web Apps</span>
          </a></li>
      <li><a href="../../../guide/webapps/best-practices.html">
            <span class="en">Best Practices for Web Apps</span>
          </a></li>
    </ul>
  </li>

  <li>
    <h2><span class="en">Appendix</span>
               <span class="de" style="display:none">Anhang</span>
               <span class="es" style="display:none">Apéndice</span>
               <span class="fr" style="display:none">Annexes</span>
               <span class="it" style="display:none">Appendice</span>
               <span class="ja" style="display:none">付録</span>
               <span class="zh-CN" style="display:none">附录</span>
               <span class="zh-TW" style="display:none">附錄</span>
    </h2>
    <ul>
      <li><a href="../../../guide/appendix/api-levels.html">
            <span class="en">Android API Levels</span>
          </a></li>
      <li><a href="../../../guide/appendix/install-location.html">
            <span class="en">App Install Location</span>
          </a></li>
      <li><a href="../../../guide/appendix/media-formats.html">
            <span class="en">Supported Media Formats <span class="new">updated</span></span>
          </a></li>
      <li><a href="../../../guide/appendix/g-app-intents.html">
            <span class="en">Intents List: Google Apps</span>
          </a></li>
      <li><a href="../../../guide/developing/tools/aidl.html">AIDL</a></li>
      <li><a href="../../../guide/appendix/glossary.html">
            <span class="en">Glossary</span>
          </a></li>
    </ul>
  </li>

</ul>

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<div class="g-unit" id="doc-content"><a name="top"></a>

<div id="jd-header" class="guide-header">
  <span class="crumb">
    &nbsp;
    
  </span>
<h1>Data Storage</h1>
</div>

  <div id="jd-content">

    <div class="jd-descr">
    <div id="qv-wrapper">
<div id="qv">

  <h2>Storage quickview</h2>
  <ul>
    <li>Use Shared Preferences for primitive data</li>
    <li>Use internal device storage for private data</li>
    <li>Use external storage for large data sets that are not private</li>
    <li>Use SQLite databases for structured storage</li>
  </ul>

  <h2>In this document</h2>
  <ol>
    <li><a href="#pref">Using Shared Preferences</a></li>
    <li><a href="#filesInternal">Using the Internal Storage</a>
      <ol>
        <li><a href="#InternalCache">Saving cache files</a></li>
        <li><a href="#InternalMethods">Other useful methods</a></li>
      </ol></li>
    <li><a href="#filesExternal">Using the External Storage</a>
      <ol>
        <li><a href="#MediaAvail">Checking media availability</a></li>
        <li><a href="#AccessingExtFiles">Accessing files on external storage</a></li>
        <li><a href="#SavingSharedFiles">Saving files that should be shared</a></li>
        <li><a href="#ExternalCache">Saving cache files</a></li>
      </ol></li>
    <li><a href="#db">Using Databases</a>
      <ol>
        <li><a href="#dbDebugging">Database debugging</a></li>
      </ol></li>
    <li><a href="#netw">Using a Network Connection</a></li>
  </ol>

  <h2>See also</h2>
  <ol>
    <li><a href="#pref">Content Providers and Content Resolvers</a></li>
  </ol>

</div>
</div>

<p>Android provides several options for you to save persistent application data. The solution you
choose depends on your specific needs, such as whether the data should be private to your
application or accessible to other applications (and the user) and how much space your data
requires.
</p>

<p>Your data storage options are the following:</p>

<dl>
  <dt><a href="#pref">Shared Preferences</a></dt>
    <dd>Store private primitive data in key-value pairs.</dd>
  <dt><a href="#filesInternal">Internal Storage</a></dt>
    <dd>Store private data on the device memory.</dd>
  <dt><a href="#filesExternal">External Storage</a></dt>
    <dd>Store public data on the shared external storage.</dd>
  <dt><a href="#db">SQLite Databases</a></dt>
    <dd>Store structured data in a private database.</dd>
  <dt><a href="#netw">Network Connection</a></dt>
    <dd>Store data on the web with your own network server.</dd>
</dl>

<p>Android provides a way for you to expose even your private data to other applications
&mdash; with a <a href="../../../guide/topics/providers/content-providers.html">content
provider</a>. A content provider is an optional component that exposes read/write access to
your application data, subject to whatever restrictions you want to impose. For more information
about using content providers, see the
<a href="../../../guide/topics/providers/content-providers.html">Content Providers</a>
documentation.
</p>




<h2 id="pref">Using Shared Preferences</h2>

<p>The <code><a href="../../../reference/android/content/SharedPreferences.html">SharedPreferences</a></code> class provides a general framework that allows you
to save and retrieve persistent key-value pairs of primitive data types. You can use <code><a href="../../../reference/android/content/SharedPreferences.html">SharedPreferences</a></code> to save any primitive data: booleans, floats, ints, longs, and
strings. This data will persist across user sessions (even if your application is killed).</p>

<div class="sidebox-wrapper">
<div class="sidebox">
<h3>User Preferences</h3>
<p>Shared preferences are not strictly for saving "user preferences," such as what ringtone a
user has chosen. If you're interested in creating user preferences for your application, see <code><a href="../../../reference/android/preference/PreferenceActivity.html">PreferenceActivity</a></code>, which provides an Activity framework for you to create
user preferences, which will be automatically persisted (using shared preferences).</p>
</div>
</div>

<p>To get a <code><a href="../../../reference/android/content/SharedPreferences.html">SharedPreferences</a></code> object for your application, use one of
two methods:</p>
<ul>
  <li><code><a href="../../../reference/android/content/Context.html#getSharedPreferences(java.lang.String, int)">getSharedPreferences()</a></code> - Use this if you need multiple preferences files identified by name,
which you specify with the first parameter.</li>
  <li><code><a href="../../../reference/android/app/Activity.html#getPreferences(int)">getPreferences()</a></code> - Use this if you need
only one preferences file for your Activity. Because this will be the only preferences file
for your Activity, you don't supply a name.</li>
</ul>

<p>To write values:</p>
<ol>
  <li>Call <code><a href="../../../reference/android/content/SharedPreferences.html#edit()">edit()</a></code> to get a <code><a href="../../../reference/android/content/SharedPreferences.Editor.html">SharedPreferences.Editor</a></code>.</li>
  <li>Add values with methods such as <code><a href="../../../reference/android/content/SharedPreferences.Editor.html#putBoolean(java.lang.String, boolean)">putBoolean()</a></code> and <code><a href="../../../reference/android/content/SharedPreferences.Editor.html#putString(java.lang.String, java.lang.String)">putString()</a></code>.</li>
  <li>Commit the new values with <code><a href="../../../reference/android/content/SharedPreferences.Editor.html#commit()">commit()</a></code></li>
</ol>

<p>To read values, use <code><a href="../../../reference/android/content/SharedPreferences.html">SharedPreferences</a></code> methods such as <code><a href="../../../reference/android/content/SharedPreferences.html#getBoolean(java.lang.String, boolean)">getBoolean()</a></code> and <code><a href="../../../reference/android/content/SharedPreferences.html#getString(java.lang.String, java.lang.String)">getString()</a></code>.</p>

<p>
Here is an example that saves a preference for silent keypress mode in a
calculator:
</p>

<pre>
public class Calc extends Activity {
    public static final String PREFS_NAME = "MyPrefsFile";

    &#64;Override
    protected void onCreate(Bundle state){
       super.onCreate(state);
       . . .

       // Restore preferences
       SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
       boolean silent = settings.getBoolean("silentMode", false);
       setSilent(silent);
    }

    &#64;Override
    protected void onStop(){
       super.onStop();

      // We need an Editor object to make preference changes.
      // All objects are from android.context.Context
      SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
      SharedPreferences.Editor editor = settings.edit();
      editor.putBoolean("silentMode", mSilentMode);

      // Commit the edits!
      editor.commit();
    }
}
</pre>




<a name="files"></a>
<h2 id="filesInternal">Using the Internal Storage</h2>

<p>You can save files directly on the device's internal storage. By default, files saved
to the internal storage are private to your application and other applications cannot access
them (nor can the user). When the user uninstalls your application, these files are removed.</p>

<p>To create and write a private file to the internal storage:</p>

<ol>
  <li>Call <code><a href="../../../reference/android/content/Context.html#openFileOutput(java.lang.String, int)">openFileOutput()</a></code> with the
name of the file and the operating mode. This returns a <code><a href="../../../reference/java/io/FileOutputStream.html">FileOutputStream</a></code>.</li>
  <li>Write to the file with <code><a href="../../../reference/java/io/OutputStream.html#write(byte[])">write()</a></code>.</li>
  <li>Close the stream with <code><a href="../../../reference/java/io/FileOutputStream.html#close()">close()</a></code>.</li>
</ol>

<p>For example:</p>

<pre>
String FILENAME = "hello_file";
String string = "hello world!";

FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
fos.write(string.getBytes());
fos.close();
</pre>

<p><code><a href="../../../reference/android/content/Context.html#MODE_PRIVATE">MODE_PRIVATE</a></code> will create the file (or replace a file of
the same name) and make it private to your application. Other modes available are: <code><a href="../../../reference/android/content/Context.html#MODE_APPEND">MODE_APPEND</a></code>, <code><a href="../../../reference/android/content/Context.html#MODE_WORLD_READABLE">MODE_WORLD_READABLE</a></code>, and <code><a href="../../../reference/android/content/Context.html#MODE_WORLD_WRITEABLE">MODE_WORLD_WRITEABLE</a></code>.</p>

<p>To read a file from internal storage:</p>

<ol>
  <li>Call <code><a href="../../../reference/android/content/Context.html#openFileInput(java.lang.String)">openFileInput()</a></code> and pass it the
name of the file to read. This returns a <code><a href="../../../reference/java/io/FileInputStream.html">FileInputStream</a></code>.</li>
  <li>Read bytes from the file with <code><a href="../../../reference/java/io/FileInputStream.html#read(byte[], int, int)">read()</a></code>.</li>
  <li>Then close the stream with  <code><a href="../../../reference/java/io/FileInputStream.html#close()">close()</a></code>.</li>
</ol>

<p class="note"><strong>Tip:</strong> If you want to save a static file in your application at
compile time, save the file in your project <code>res/raw/</code> directory. You can open it with
<code><a href="../../../reference/android/content/res/Resources.html#openRawResource(int)">openRawResource()</a></code>, passing the <code>R.raw.<em>&lt;filename&gt;</em></code> resource ID. This method returns an <code><a href="../../../reference/java/io/InputStream.html">InputStream</a></code>
that you can use to read the file (but you cannot write to the original file).
</p>


<h3 id="InternalCache">Saving cache files</h3>

<p>If you'd like to cache some data, rather than store it persistently, you should use <code><a href="../../../reference/android/content/Context.html#getCacheDir()">getCacheDir()</a></code> to open a <code><a href="../../../reference/java/io/File.html">File</a></code> that represents the internal directory where your application should save
temporary cache files.</p>

<p>When the device is
low on internal storage space, Android may delete these cache files to recover space. However, you
should not rely on the system to clean up these files for you. You should always maintain the cache
files yourself and stay within a reasonable limit of space consumed, such as 1MB. When the user
uninstalls your application, these files are removed.</p>


<h3 id="InternalMethods">Other useful methods</h3>

<dl>
  <dt><code><a href="../../../reference/android/content/Context.html#getFilesDir()">getFilesDir()</a></code></dt>
    <dd>Gets the absolute path to the filesystem directory where your internal files are saved.</dd>
  <dt><code><a href="../../../reference/android/content/Context.html#getDir(java.lang.String, int)">getDir()</a></code></dt>
    <dd>Creates (or opens an existing) directory within your internal storage space.</dd>
  <dt><code><a href="../../../reference/android/content/Context.html#deleteFile(java.lang.String)">deleteFile()</a></code></dt>
    <dd>Deletes a file saved on the internal storage.</dd>
  <dt><code><a href="../../../reference/android/content/Context.html#fileList()">fileList()</a></code></dt>
    <dd>Returns an array of files currently saved by your application.</dd>
</dl>




<h2 id="filesExternal">Using the External Storage</h2>

<p>Every Android-compatible device supports a shared "external storage" that you can use to
save files. This can be a removable storage media (such as an SD card) or an internal
(non-removable) storage. Files saved to the external storage are world-readable and can
be modified by the user when they enable USB mass storage to transfer files on a computer.</p>

<p class="caution"><strong>Caution:</strong> External files can disappear if the user mounts the
external storage on a computer or removes the media, and there's no security enforced upon files you
save to the external storage. All applications can read and write files placed on the external
storage and the user can remove them.</p>


<h3 id="MediaAvail">Checking media availability</h3>

<p>Before you do any work with the external storage, you should always call <code><a href="../../../reference/android/os/Environment.html#getExternalStorageState()">getExternalStorageState()</a></code> to check whether the media is available. The
media might be mounted to a computer, missing, read-only, or in some other state. For example,
here's how you can check the availability:</p>

<pre>
boolean mExternalStorageAvailable = false;
boolean mExternalStorageWriteable = false;
String state = Environment.getExternalStorageState();

if (Environment.MEDIA_MOUNTED.equals(state)) {
    // We can read and write the media
    mExternalStorageAvailable = mExternalStorageWriteable = true;
} else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
    // We can only read the media
    mExternalStorageAvailable = true;
    mExternalStorageWriteable = false;
} else {
    // Something else is wrong. It may be one of many other states, but all we need
    //  to know is we can neither read nor write
    mExternalStorageAvailable = mExternalStorageWriteable = false;
}
</pre>

<p>This example checks whether the external storage is available to read and write. The
<code><a href="../../../reference/android/os/Environment.html#getExternalStorageState()">getExternalStorageState()</a></code> method returns other states that you
might want to check, such as whether the media is being shared (connected to a computer), is missing
entirely, has been removed badly, etc. You can use these to notify the user with more information
when your application needs to access the media.</p>


<h3 id="AccessingExtFiles">Accessing files on external storage</h3>

<p>If you're using API Level 8 or greater, use <code><a href="../../../reference/android/content/Context.html#getExternalFilesDir(java.lang.String)">getExternalFilesDir()</a></code> to open a <code><a href="../../../reference/java/io/File.html">File</a></code> that represents the external storage directory where you should save your
files. This method takes a <code>type</code> parameter that specifies the type of subdirectory you
want, such as <code><a href="../../../reference/android/os/Environment.html#DIRECTORY_MUSIC">DIRECTORY_MUSIC</a></code> and
<code><a href="../../../reference/android/os/Environment.html#DIRECTORY_RINGTONES">DIRECTORY_RINGTONES</a></code> (pass <code>null</code> to receive
the root of your application's file directory). This method will create the
appropriate directory if necessary. By specifying the type of directory, you
ensure that the Android's media scanner will properly categorize your files in the system (for
example, ringtones are identified as ringtones and not music). If the user uninstalls your
application, this directory and all its contents will be deleted.</p>

<p>If you're using API Level 7 or lower, use <code><a href="../../../reference/android/os/Environment.html#getExternalStorageDirectory()">getExternalStorageDirectory()</a></code>, to open a <code><a href="../../../reference/java/io/File.html">File</a></code> representing the root of the external storage. You should then write your data in the
following directory:</p>
<pre class="no-pretty-print classic">
/Android/data/<em>&lt;package_name&gt;</em>/files/
</pre>
<p>The <code><em>&lt;package_name&gt;</em></code> is your Java-style package name, such as "<code>com.example.android.app</code>". If the user's device is running API Level 8 or greater and they
uninstall your application, this directory and all its contents will be deleted.</p>


<div class="sidebox-wrapper" style="margin-top:3em">
<div class="sidebox">

<h4>Hiding your files from the Media Scanner</h4>

<p>Include an empty file named <code>.nomedia</code> in your external files directory (note the dot
prefix in the filename). This will prevent Android's media scanner from reading your media
files and including them in apps like Gallery or Music.</p>

</div>
</div>


<h3 id="SavingSharedFiles">Saving files that should be shared</h3>

<p>If you want to save files that are not specific to your application and that should <em>not</em>
be deleted when your application is uninstalled, save them to one of the public directories on the
external storage. These directories lay at the root of the external storage, such as <code>Music/</code>, <code>Pictures/</code>, <code>Ringtones/</code>, and others.</p>

<p>In API Level 8 or greater, use <code><a href="../../../reference/android/os/Environment.html#getExternalStoragePublicDirectory(java.lang.String)">getExternalStoragePublicDirectory()</a></code>, passing it the type of public directory you want, such as
<code><a href="../../../reference/android/os/Environment.html#DIRECTORY_MUSIC">DIRECTORY_MUSIC</a></code>, <code><a href="../../../reference/android/os/Environment.html#DIRECTORY_PICTURES">DIRECTORY_PICTURES</a></code>,
<code><a href="../../../reference/android/os/Environment.html#DIRECTORY_RINGTONES">DIRECTORY_RINGTONES</a></code>, or others. This method will create the
appropriate directory if necessary.</p>

<p>If you're using API Level 7 or lower, use <code><a href="../../../reference/android/os/Environment.html#getExternalStorageDirectory()">getExternalStorageDirectory()</a></code> to open a <code><a href="../../../reference/java/io/File.html">File</a></code> that represents
the root of the external storage, then save your shared files in one of the following
directories:</p>

<ul class="nolist"></li>
  <li><code>Music/</code> - Media scanner classifies all media found here as user music.</li>
  <li><code>Podcasts/</code> - Media scanner classifies all media found here as a podcast.</li>
  <li><code>Ringtones/ </code> - Media scanner classifies all media found here as a ringtone.</li>
  <li><code>Alarms/</code> - Media scanner classifies all media found here as an alarm sound.</li>
  <li><code>Notifications/</code> - Media scanner classifies all media found here as a notification
sound.</li>
  <li><code>Pictures/</code> - All photos (excluding those taken with the camera).</li>
  <li><code>Movies/</code> - All movies (excluding those taken with the camcorder).</li>
  <li><code>Download/</code> - Miscellaneous downloads.</li>
</ul>


<h3 id="ExternalCache">Saving cache files</h3>

<p>If you're using API Level 8 or greater, use <code><a href="../../../reference/android/content/Context.html#getExternalCacheDir()">getExternalCacheDir()</a></code> to open a <code><a href="../../../reference/java/io/File.html">File</a></code> that represents the
external storage directory where you should save cache files. If the user uninstalls your
application, these files will be automatically deleted. However, during the life of your
application, you should manage these cache files and remove those that aren't needed in order to
preserve file space.</p>

<p>If you're using API Level 7 or lower, use <code><a href="../../../reference/android/os/Environment.html#getExternalStorageDirectory()">getExternalStorageDirectory()</a></code> to open a <code><a href="../../../reference/java/io/File.html">File</a></code> that represents
the root of the external storage, then write your cache data in the following directory:</p>
<pre class="no-pretty-print classic">
/Android/data/<em>&lt;package_name&gt;</em>/cache/
</pre>
<p>The <code><em>&lt;package_name&gt;</em></code> is your Java-style package name, such as "<code>com.example.android.app</code>".</p>



<h2 id="db">Using Databases</h2>

<p>Android provides full support for <a href="http://www.sqlite.org/">SQLite</a> databases.
Any databases you create will be accessible by name to any
class in the application, but not outside the application.</p>

<p>The recommended method to create a new SQLite database is to create a subclass of <code><a href="../../../reference/android/database/sqlite/SQLiteOpenHelper.html">SQLiteOpenHelper</a></code> and override the <code><a href="../../../reference/android/database/sqlite/SQLiteOpenHelper.html#onCreate(android.database.sqlite.SQLiteDatabase)">onCreate()</a></code> method, in which you
can execute a SQLite command to create tables in the database. For example:</p>

<pre>
public class DictionaryOpenHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 2;
    private static final String DICTIONARY_TABLE_NAME = "dictionary";
    private static final String DICTIONARY_TABLE_CREATE =
                "CREATE TABLE " + DICTIONARY_TABLE_NAME + " (" +
                KEY_WORD + " TEXT, " +
                KEY_DEFINITION + " TEXT);";

    DictionaryOpenHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    &#64;Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL(DICTIONARY_TABLE_CREATE);
    }
}
</pre>

<p>You can then get an instance of your <code><a href="../../../reference/android/database/sqlite/SQLiteOpenHelper.html">SQLiteOpenHelper</a></code>
implementation using the constructor you've defined. To write to and read from the database, call
<code><a href="../../../reference/android/database/sqlite/SQLiteOpenHelper.html#getWritableDatabase()">getWritableDatabase()</a></code> and <code><a href="../../../reference/android/database/sqlite/SQLiteOpenHelper.html#getReadableDatabase()">getReadableDatabase()</a></code>, respectively. These both return a
<code><a href="../../../reference/android/database/sqlite/SQLiteDatabase.html">SQLiteDatabase</a></code> object that represents the database and
provides methods for SQLite operations.</p>

<div class="sidebox-wrapper">
<div class="sidebox">
<p>Android does not impose any limitations beyond the standard SQLite concepts. We do recommend
including an autoincrement value key field that can be used as a unique ID to
quickly find a record.  This is not required for private data, but if you
implement a <a href="../../../guide/topics/providers/content-providers.html">content provider</a>,
you must include a unique ID using the <code><a href="../../../reference/android/provider/BaseColumns.html#_ID">BaseColumns._ID</a></code>
constant.
</p>
</div>
</div>

<p>You can execute SQLite queries using the <code><a href="../../../reference/android/database/sqlite/SQLiteDatabase.html">SQLiteDatabase</a></code>
<code><a href="../../../reference/android/database/sqlite/SQLiteDatabase.html#query(boolean, java.lang.String, java.lang.String[], java.lang.String, java.lang.String[], java.lang.String, java.lang.String, java.lang.String, java.lang.String)">query()</a></code> methods, which accept various query parameters, such as the table to query,
the projection, selection, columns, grouping, and others. For complex queries, such as
those that require column aliases, you should use
<code><a href="../../../reference/android/database/sqlite/SQLiteQueryBuilder.html">SQLiteQueryBuilder</a></code>, which provides
several convienent methods for building queries.</p>

<p>Every SQLite query will return a <code><a href="../../../reference/android/database/Cursor.html">Cursor</a></code> that points to all the rows
found by the query. The <code><a href="../../../reference/android/database/Cursor.html">Cursor</a></code> is always the mechanism with which
you can navigate results from a database query and read rows and columns.</p>

<p>For sample apps that demonstrate how to use SQLite databases in Android, see the
<a href="../../../resources/samples/NotePad/index.html">Note Pad</a> and
<a href="../../../resources/samples/SearchableDictionary/index.html">Searchable Dictionary</a>
applications.</p>


<h3 id="dbDebugging">Database debugging</h3>

<p>The Android SDK includes a <code>sqlite3</code> database tool that allows you to browse
table contents, run SQL commands, and perform other useful functions on SQLite
databases.  See <a href="../../../guide/developing/tools/adb.html#sqlite">Examining sqlite3
databases from a remote shell</a> to learn how to run this tool.
</p>





<h2 id="netw">Using a Network Connection</h2>

<!-- TODO MAKE THIS USEFUL!! -->

<p>You can use the network (when it's available) to store and retrieve data on your own web-based
services. To do network operations, use classes in the following packages:</p>

<ul class="no-style">
  <li><code><code><a href="../../../reference/java/net/package-summary.html">java.net.*</a></code></code></li>
  <li><code><code><a href="../../../reference/android/net/package-summary.html">android.net.*</a></code></code></li>
</ul>

    </div>

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